Sesame Meal: The Ideal Alternative to Soybean Meal for Fattening Beef Cattle—Reducing Nitrogen Excretion and Bolstering Antioxidant Defenses

Sesame meal possesses high crude protein content (40-50%), abundant methionine, and natural antioxidant components such as lignan compounds, making it a high-quality feed alternative to soybean meal in ruminant production. This study systematically evaluated the effects of completely replacing soybean meal with sesame meal in the diet on growth performance, serum biochemistry, antioxidant activity, rumen fermentation parameters, and microbial composition in finishing beef cattle. The trial employed a completely randomised design, selecting 18 Angus bulls with similar initial body weights (566.7 ± 38.1 kg). Animals were randomly assigned to the SBM group (<i>n</i> = 9) and SSM group (<i>n</i> = 9), with a 7-day pre-trial period followed by a 96-day main trial period. Results indicate that replacing soybean meal with sesame meal significantly enhances the antioxidant capacity of fattening beef cattle. Catalase (CAT) activity markedly increased (<i>p</i> < 0.05), while glutathione peroxidase activity showed an upward trend (0.05 < <i>p</i> < 0.1). This improvement was accompanied by a substantial shift in rumen microbial composition, highlighted by a marked enrichment of beneficial bacteria including p_Verrucomicrobiota, p_Spirochaetota, <i>g_CAG_352</i>, <i>norank_f_Lachnospiraceae</i>, and <i>g_Rikenellaceae_RC9_gut_group</i>, which collectively contributed to greater microbial complexity and stability. Regarding nitrogen metabolism, urinary nitrogen and serum urea nitrogen levels were significantly reduced in the sesame meal group (<i>p</i> < 0.05), indicating improved nitrogen utilization efficiency. Overall, completely replacing soybean meal with sesame meal in the diet of finishing beef cattle did not adversely affect growth and slaughter performance. It simultaneously significantly enhanced antioxidant capacity, reduced urinary nitrogen excretion, and lowered feed costs. These findings underscore the potential of sesame meal as a sustainable, nutritionally advantageous alternative for optimising beef cattle diets.